This invention relates to point-of-use purification systems and, more particularly, to an automatic control system with a water purification system. Preferably, the system is a point-of-use ultrafiltration system including controls for purge, rinse-up and purge, or sanitization, rinse-up and purge.
Point-of-use systems overcome the contamination problems encountered because of internal piping contamination occurring in installations having a central processing facility with piping from the facility to the point of use. The degree of filtration accomplished by the present invention is dependent upon the pore size of the membrane of the filtration cartridge employed with the invention. Ultrafiltration is the preferred process utilized because of the wide range of applications for ultrafiltered water.
Generally accepted definitions in the area are as follows: A membrane filter having a pore size range of from 0.001 to 0.1 microns is used in ultrafiltration. Filters having a pore size greater than 0.1 microns are used in microfiltration and filters having pore size smaller than 0.001 microns are used in hyperfiltration (reverse osmosis) processes. It will of course be understood that there are no precise lines of demarcation among the classes of filters and some overlap of pore size may and frequently will occur.
A point-of-use system producing ultrafiltered water is preferred because of cost/effect considerations and the wide variety of uses of ultrafiltered water. For example, the ultrafiltration process results in a product useful for the upgrading of D.I. (deionized) water for semiconductor rinsing because the product is free of contaminants such as pyrogens, particulates, colloids and high molecular weight organic materials. The ultrafiltration process is useful in may separation applications such as: pre-treatment of water for central D.I. and reverse osmosis systems; depyrogenation of water for chemical and biological laboratories; particulate and pyrogen removal from D.I. water to be used for analytical procedures; production of pyrogen free water for biotechnology and tissue culture; preparation of clinical samples for analysis; concentration of bacterial and mammalian cells; depyrogenation of certain parenteral solutions such as antibiotics, buffers and sugar solutions; and pretreatment of feed water for distillation units to minimize scale buildup and prolong equipment life.
An essential point of this invention is to provide a filtration system including automatic controls for minimizing the possibility for human error. Further, the system includes a control for automatically directing contaminants and a predetermined volume percentage of water from the bottom of the system filter to waste every time the system product valve is opened.
Essential and otherwise known art procedures performed periodically in point-of-use filtration systems of the type under discussion include purge, rinse-up and sanitization. Purging is the controlled flushing of the upstream side of the filter membrane to ensure removal of any accumulated reject materials. Rinse-up refers to controlled, periodic passage of liquid through the filter unit to assure stagnation does not take place within the unit. Sanitization concerns periodic treatment to kill and remove any bacteria in the filter unit.
In the present invention, the procedures just outlined may be performed in various combinations at predetermined intervals so that product liquid or water of acceptable quality is readily available upon demand. Further, one automatic control system of the invention also provides for opening of a filter reject valve every time the system product valve is opened in order to minimize excessive loss of pretreated fluid which occurs with manually operated systems.